Surfactants are compounds which are used to change the surface chemistry and, in particular, the surface tension, of liquids. Many surfactants are formed in a liquid-phase reaction wherein the liquid phase is often the solvent, such as 1,4-dioxane (diethylene ether, hereinafter "dioxane"). Recent evidence indicates that dioxane is carcinogenic, even when present in very small concentrations. Consequently, use of surfactants in consumer products generally requires that the surfactants substantially be decontaminated of dioxane. For example, products to which plants or animals are exposed generally must have a dioxane content of less than about five parts per million. Pharmaceutical and cosmetic requirements are even more strict, limiting dioxane contents in products to less than about 0.5 parts per million.
Several attempts to remove dioxane from surfactants have been made. In one method, dioxane is removed by vacuum stripping the dioxane from the surfactant. However, vacuum stripping and other distillation-like methods commonly result in excessive foaming by the surfactant during volatilization of the dioxane. Prolonged heating of the surfactant can reduce the amount of foaming, but typically will also cause significant decomposition of the surfactant.
In another method, dioxane is removed from the surfactant by partitioning with an appropriate organic solvent, which can extract the dioxane. However, a portion of the organic solvent typically remains in the surfactant. Removal of the residual organic solvent from the surfactant is generally difficult and expensive.